Toll-like receptor 2 and Toll-like receptor 4 (TLR2 and TLR4)

Toll-like receptor 2 (TLR2) and toll-like receptor 4 (TLR4) are type I transmembrane pattern recognition receptors expressed on cells of both innate (e.g., macrophages, neutrophils) and adaptive immunity. They recognize distinct pathogen-associated molecular patterns from bacteria—TLR2 primarily detects glycolipids/lipoproteins from Gram-positive bacteria while TLR4 recognizes lipopolysaccharide from Gram-negative bacteria. Upon ligand binding, they initiate intracellular signaling cascades through adaptor proteins such as MyD88 or TRIF. This leads to nuclear factor kappa B (NF-kB), mitogen activated protein kinase (MAPK), AP‑1 transcription factor activation, pro-inflammatory cytokine production—including TNF-alpha and interleukins—and modulation of chemokine receptors like CCR1/CCR2 on monocytes/macrophages[1][3][4]. These processes play central roles in host defense but can also contribute to chronic inflammation if dysregulated. Note: The original query describes a process ("macrophage activation via...") rather than a discrete molecular target; thus "Toll-like receptor 2" and "Toll-like receptor 4" should be used as canonical targets for structured data extraction purposes rather than the broader pathway/process itself.

Other names

Toll-like receptor 2Toll-like receptor 4TLR-2TLR-4

Agonists activate innate immune signaling by binding to extracellular domains of the receptors. Activation leads to downstream MyD88-dependent or TRIF-dependent pathways resulting in NF-kB and MAPK activation[3][4].